Various mounting structures are known in the prior art for mounting the propeller to the propeller shaft and absorbing shock when the propeller strikes an object, to protect the propeller shaft and the drive.
Conover U.S. Pat. No. 2,125,270 shows a cup-shaped annulus 10 keyed to propeller shaft 4 by shear pin 11 and having an outer rubber block 15 engaging the propeller hub and absorbing shock.
Yantis U.S. Pat. No. 2,164,485 shows a shear pin 28, and rubber shock absorbing drive sleeve 18, FIG. 2, sleeve 36, FIG. 6, sleeve 44, FIG. 10, and sleeve 60, FIG. 13.
Hartz U.S. Pat. No. 2,633,923 shows a helical spring clutch element carried by the propeller shaft in radial frictional engagement with the hub and disposed so that engagement is relaxed upon overload when the propeller strikes an underwater object.
Stewart U.S. Pat. No. 3,230,739 shows a slip clutch with a cylindrical shaped flexible elastomeric member 28.
Marconi, Jr. U.S. Pat. No. 3,321,024 shows a resilient rubber or the like bushing 46, wherein slippage may occur between shank 36 and bushing 46 and between bushing 46 and aperture 18.
Schiek U.S. Pat. No. 4,317,655 shows rubber shock hub 28.
Carmel U.S. Pat. No. 4,338,064 shows a clutch assembly with a pair of elastomeric cushions 32.
Fishbaugh et al U.S. Pat. No. 4,452,591 shows rubber member 17 between inner rotary member 14 and propeller hub 13.
Costabile et al U.S. Pat. No. 4,566,855 shows a three piece break-away blade propeller. The break-away blade will break free of the blade support sections if the propeller blade strikes an obstacle. Costabile et al also shows in FIGS. 9-12 a resilient shock mount sleeve 92.
Frazzell et al U.S. Pat. No. 4,642,057 shows a cushion member 16 between sleeve member 14 and propeller hub 17.
Karls U.S. Pat. No. 5,022,875 shows rubber torsional shock dampening member 38 providing limited slip and preventing propeller breakage upon striking underwater objects.